De Gea was criticised for a punch that eventually allowed Clint Dempsey to snatch an injury-time equaliser for Tottenham last weekend.
But Schmeichel, who made almost 300 appearances for the Old Trafford club, believes Sir Alex Ferguson's side would have lost the White Hart Lane contest had it not been for the Spaniard, pointing the finger instead at those in front of him.
"It is very easy to claim De Gea is to blame," said Schmeichel.
"I disagree. I think if De Gea had not played the way he did we would have lost 4-1.
"We played in a way that required the goalkeeper to make saves. He did that. He did his job. Nobody is highlighting that.
"My point is that if you are not that deep, we are not conceding those chances. That is the thing I would work on.
"In general, the way to win championships is not by defending as deeply as we did for the final hour on Sunday.
"For the goal, David does all the right things. He got a fist to it under pressure but, unfortunately, the ball ends up with a Spurs player.
"We should be further up the pitch. If that starts with the goalkeeper, he needs to work on that, but we need them to be brave enough to take them out."